Are there differences between young African-American and European-American women in the relative influences of genetics versus environment on age at first drink and problem alcohol use?

Developmental genetic effects on externalizing behavior and alcohol use: Examination across two longitudinal samples

Externalizing behavior in early adolescence is associated with alcohol use in adolescence and early adulthood and these behaviors often emerge as part of a developmental sequence. This pattern can be the result of heterotypic continuity, in which different behaviors emerge over time based on an underlying shared etiology. In particular, there is largely a shared genetic etiology underlying externalizing and substance use behaviors. We examined whether polygenic risk for alcohol use disorder predicted (1) externalizing behavior in early adolescence and alcohol use in adolescence in the Early Steps Multisite sample and (2) externalizing behavior in adolescence and alcohol use in early adulthood in the Project Alliance 1 (PAL1) sample. We examined associations separately for African Americans and European Americans. When examining European Americans in the Early Steps sample, greater polygenic risk was associated with externalizing behavior in early adolescence. In European Americans in PAL1, we found greater polygenic risk was associated with alcohol use in early adulthood. Effects were largely absent in African Americans in both samples. Results imply that genetic predisposition for alcohol use disorder may increase risk for externalizing and alcohol use as these behaviors emerge developmentally.

Age varying polygenic effects on alcohol use in African Americans and European Americans from adolescence to adulthood

Genetic effects on alcohol use can vary over time but are often examined using longitudinal models that predict a distal outcome at a single time point. The vast majority of these studies predominately examine effects using White, European American (EA) samples or examine the etiology of genetic variants identified from EA samples in other racial/ethnic populations, leading to inconclusive findings about genetic effects on alcohol use. The current study examined how genetic influences on alcohol use varied by age across a 15 year period within a diverse ethnic/racial sample of adolescents. Using a multi-ethnic approach, polygenic risk scores were created for African American (AA, n = 192) and EA samples (n = 271) based on racially/ethnically aligned genome wide association studies. Age-varying associations between polygenic scores and alcohol use were examined from age 16 to 30 using time-varying effect models separately for AA and EA samples. Polygenic risk for alcohol use was found to be associated with alcohol use from age 22-27 in the AA sample and from age 24.50 to 29 in the EA sample. Results are discussed relative to the intersection of alcohol use and developmental genetic effects in diverse populations.

Genome-wide admixture mapping of DSM-IV alcohol dependence, criterion count, and the self-rating of the effects of ethanol in African American populations

African Americans (AA) have lower prevalence of alcohol dependence and higher subjective response to alcohol than European Americans. Genome-wide association studies (GWAS) have identified genes/variants associated with alcohol dependence specifically in AA; however, the sample sizes are still not large enough to detect variants with small effects. Admixture mapping is an alternative way to identify alcohol dependence genes/variants that may be unique to AA. In this study, we performed the first admixture mapping of DSM-IV alcohol dependence diagnosis, DSM-IV alcohol dependence criterion count, and two scores from the self-rating of effects of ethanol (SRE) as measures of response to alcohol: the first five times of using alcohol (SRE-5) and average of SRE across three times (SRE-T). Findings revealed a region on chromosome 4 that was genome-wide significant for SRE-5 (p value = 4.18E-05). Fine mapping did not identify a single causal variant to be associated with SRE-5; instead, conditional analysis concluded that multiple variants collectively explained the admixture mapping signal. PPARGC1A, a gene that has been linked to alcohol consumption in previous studies, is located in this region. Our finding suggests that admixture mapping is a useful tool to identify genes/variants that may have been missed by current GWAS approaches in admixed populations.

Childhood Trauma and Two Stages of Alcohol Use in African American and European American Women: Findings from a Female Twin Sample

The current investigation assessed for moderating effects of childhood trauma on genetic and environmental contributions to timing of alcohol use initiation and alcohol use disorder in African American (AA) and European American (EA) women. Data were drawn from diagnostic telephone interviews conducted with 3786 participants (14.6% AA) in a longitudinal female twin study. Childhood trauma was defined alternately as child maltreatment and more broadly to include other events (e.g., witnessing violence). Phenotypic associations between childhood trauma and alcohol outcomes were estimated using logistic regression analyses. Twin modeling was conducted to test for moderating effects of childhood trauma on the contributions of genetic and environmental factors to timing of initiation and alcohol use disorder. Under both definitions, childhood trauma was associated with early initiation (relative risk ratios: 1.90, 1.72) and alcohol use disorder (odds ratios: 1.92, 1.76). Yet gene by environment effects were observed only for child maltreatment and timing of initiation in EA women, with heritable influences less prominent in those who had experienced child maltreatment (0.35, 95% CI: 0.05-0.66 vs. 0.52, 95% CI: 0.30-0.73). We found more similarities than differences in the association of childhood trauma with alcohol outcomes across racial/ethnic groups, trauma type, and stages of alcohol use. However, findings suggest that the relative contribution of genetic factors to alcohol outcomes differs by childhood maltreatment history in EA women specifically in the earliest stage of alcohol use.

Problematic alcohol use associates with sodium channel and clathrin linker 1 (SCLT1) in trauma-exposed populations

Excessive alcohol use is extremely prevalent in the United States, particularly among trauma-exposed individuals. While several studies have examined genetic influences on alcohol use and related problems, this has not been studied in the context of trauma-exposed populations. We report results from a genome-wide association study of alcohol consumption and associated problems as measured by the alcohol use disorders identification test (AUDIT) in a trauma-exposed cohort. Results indicate a genome-wide significant association between total AUDIT score and rs1433375 [N = 1036, P = 2.61 × 10^-8 (dominant model), P = 7.76 × 10^-8 (additive model)], an intergenic single-nucleotide polymorphism located 323 kb upstream of the sodium channel and clathrin linker 1 (SCLT1) at 4q28. rs1433375 was also significant in a meta-analysis of two similar, but independent, cohorts (N = 1394, P = 0.0004), the Marine Resiliency Study and Systems Biology PTSD Biomarkers Consortium. Functional analysis indicated that rs1433375 was associated with SCLT1 gene expression and cortical-cerebellar functional connectivity measured via resting state functional magnetic resonance imaging. Together, findings suggest a role for sodium channel regulation and cerebellar functioning in alcohol use behavior. Identifying mechanisms underlying risk for problematic alcohol use in trauma-exposed populations is critical for future treatment and prevention efforts.

Childhood interpersonal violence and adult alcohol, cannabis, and tobacco use disorders: variation by race/ethnicity?

BACKGROUND

Exposure to child maltreatment has been shown to increase lifetime risk for substance use disorders (SUD). However, this has not been systematically examined among race/ethnic groups, for whom rates of exposure to assaultive violence and SUD differ. This study examined variation by race/ethnicity and gender in associations of alcohol (AUD), cannabis (CUD), and tobacco (TUD) use disorders with three types of childhood interpersonal violence (cIPV): physical abuse, sexual abuse, and witnessing parental violence.

METHOD

Data from the National Epidemiologic Survey of Alcohol-Related Conditions-III (N: 36 309), a US nationally representative sample, was utilized to examine associations of DSM-5 AUD, CUD and TUD with cIPV among men and women of five racial/ethnic groups. Models were adjusted for additional risk factors (e.g. parental substance use problems, participant's co-occurring SUD).

RESULTS

Independent contributions of childhood physical and sexual abuse to AUD, CUD, and TUD, and of witnessing parental violence to AUD and TUD were observed. Associations of cIPV and SUD were relatively similar across race/ethnicity and gender [Odds Ratios (ORs) ranged from 1.1 to 1.9], although associations of physical abuse with AUD and TUD were greater among males, associations of parental violence and AUD were greater among females, and associations of parental violence with AUD were greater among Hispanic women and American Indian men.

CONCLUSIONS

Given the paucity of research in this area, and the potential identification of modifiable risk factors to reduce the impact of childhood interpersonal violence on SUDs, further research and consideration of tailoring prevention and intervention efforts to different populations are warranted.

Genes involved in stress response and alcohol use among high-risk African American youth

BACKGROUND

Genetic and environmental factors influence substance use behaviors in youth. One of the known environmental risk factors is exposure to life stressors. The aim of this project is to study the interaction between NR3C1 and CRHBP, genes thought to be involved in stress pathways, exposure to stressful life events, and adolescent alcohol use/misuse.

METHODS

The sample included 541 African American individuals (ages 13-18) from the Genes, Environment, and Neighborhood Initiative, a subset of the Mobile Youth Survey sample from whom DNA and more extensive phenotypic data were collected. Participants were selected from high-poverty neighborhoods in Mobile, Alabama, with potential exposure to a variety of extreme life stressors.

RESULTS

A measure of stressful life events was significantly predictive of alcohol use/misuse. In addition, this association was significantly dependent upon the number of putative risk variants at rs1715749, a single-nucleotide polymorphism (SNP) in CRHBP (P ≤ .006). There was no significant interaction between NR3C1 and stressful life events with respect to alcohol use/misuse, after taking into account multiple testing.

CONCLUSIONS

These findings suggest that CRHBP variants are potentially relevant for adolescent alcohol use/misuse among African American youth populations being reared within the context of stressful life events and warrant replication.

Age of Drinking Initiation as a Risk Factor for Alcohol Use Disorder Symptoms is Moderated by ALDH2*2 and Ethnicity

BACKGROUND

An early age of drinking initiation (ADI) has been associated with increased risk for alcohol use disorders (AUDs), but the consistency of this risk across diverse samples has not been well studied. The purpose of this study was to examine whether the pathway from ADI to AUD symptoms by early adulthood is moderated by ethnicity and possessing an alcohol-metabolizing gene ALDH2*2 variant allele.

METHODS

We used multigroup structural equation modeling, including 5 groups split by ethnicity and ALDH2*2, to examine the consistency of the path from ADI to AUD symptoms in 604 Chinese-, Korean-, and White-American college students. We further examined the effects of ALDH2*2, ethnicity, and their interaction in Asians to better understand their unique contributions to the moderation.

RESULTS

The association between ADI and AUD symptoms was moderated, with ADI negatively associated with AUD symptoms among Koreans without ALDH2*2 and Whites, but not among Koreans with ALDH2*2 or Chinese regardless of ALDH2*2. Both ALDH2*2 and ethnicity within Asians contributed unique variability in the effect.

CONCLUSIONS

Ethnicity and ALDH2*2 altered the relationship of ADI as a risk factor for AUD symptoms. Being Chinese and possessing an ALDH2*2 allele within Koreans both buffered against the risk for AUD symptoms associated with earlier ADI, indicating that this relationship can be attenuated by protective factors.

Review: Genetic research on alcohol use outcomes in African American populations: A review of the literature, associated challenges, and implications

BACKGROUND AND OBJECTIVES

There have been remarkable advances in understanding genetic influences on complex traits; however, individuals of African descent have been underrepresented in genetic research.

METHODS

We review the limitations of existing genetic research on alcohol phenotypes in African Americans (AA) including both twin and gene identification studies, possible reasons for underrepresentation of AAs in genetic research, the implications of the lack of racially diverse samples, and special considerations regarding conducting genetic research in AA populations.

RESULTS

There is a marked absence of large-scale AA twin studies so little is known about the genetic epidemiology of alcohol use and problems among AAs. Individuals of African descent have also been underrepresented in gene identification efforts; however, there have been recent efforts to enhance representation. It remains unknown the extent to which genetic variants associated with alcohol use outcomes in individuals of European and African descent will be shared. Efforts to increase representation must be accompanied by careful attention to the ethical, legal, and social implications of genetic research. This is particularly true for AAs due to the history of abuse by the biomedical community and the persistent racial discrimination targeting this population.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Lack of representation in genetic studies limits our understanding of the etiological factors that contribute to substance use and psychiatric outcomes in populations of African descent and has the potential to further perpetuate health disparities. Involving individuals of diverse ancestry in discussions about genetic research will be critical to ensure that all populations benefit equally from genetic advances. (Am J Addict 2017;26:486-493).

The Rate of Change in Alcohol Misuse Across Adolescence is Heritable

BACKGROUND

Alcohol use typically begins during adolescence and escalates into young adulthood. This represents an important period for the establishment of alcohol use and misuse patterns, which can have psychosocial and medical consequences. Although changes in alcohol use during this time have been phenotypically characterized, their genetic nature is poorly understood.

METHODS

Participants of the Avon Longitudinal Study of Parents and Children completed the Alcohol Use Disorders Identification Test (AUDIT) 4 times from age 16 to 20. We used Mplus to construct a growth model characterizing changes in AUDIT scores across time (N = 4,545, where data were available for at least 2 time points). The slope of the model was used as the phenotype in a genomewide association study (N = 3,380), followed by secondary genetic analyses.

RESULTS

No individual marker met genomewide significance criteria. Top markers mapped to biologically plausible candidate genes. The slope term was moderately heritable (h²_SNP = 0.26, p = 0.009), and replication attempts using a meta-analysis of independent samples provided support for implicated variants at the aggregate level. Nominally significant (p < 0.00001) markers mapped to putatively active genomic regions in brain tissue more frequently than expected by chance.

CONCLUSIONS

These results build on prior studies by demonstrating that common genetic variation impacts alcohol misuse trajectories. Influential loci map to genes that merit additional research, as well as to intergenic regions with regulatory functions in the central nervous system. These findings underscore the complex biological nature of alcohol misuse across development.

Is 'age at first drink' a useful concept in alcohol research and prevention? We doubt that

AIM

To address and discuss the weaknesses of age at first drink (AFD) as a concept in alcohol research and prevention.

METHODS

Narrative literature review.

RESULTS

Varying from one sip to the consumption of several full drinks, and sometimes including the specification of particular conditions (e.g. without parental consent), no exact definition and operationalization of AFD was found. Evidence reveals poor test-retest reliability when the same individuals report their AFD two or more times. Theoretical arguments and empirical evidence fail to explain why having one sip or one drink earlier than peers should cause heavier drinking and related problems later in life. Alternative explanations such as self-selection, third variable effects and systematic report bias are not considered in most studies. These shortcomings also make AFD unsuitable as an indicator or marker of underlying problems such as conduct problems and academic failure. Together with unjustified causal inferences, this has led to an over-emphasis on the relevance of postponing AFD as a way to prevent problems later in life.

CONCLUSION

We argue in favour of shifting the focus of alcohol research and prevention away from AFD towards a better understanding of the progression from infrequent, low-quantity drinking to more detrimental drinking patterns and the prevention of associated acute and short-term harm.

Early onset alcohol use and self-harm: a discordant twin analysis

BACKGROUND

Self-harm has considerable societal and economic costs and has been extensively studied in relation to alcohol involvement. Although early onset alcohol use (EAU) has been causally linked to maladaptive clinical outcomes, its association with self-harm is less well characterized. This study aimed to further examine the link between EAU and both nonsuicidal self-injury (NSSI) and suicide attempt (SA), and elucidate shared familial and causal/individual-specific pathways that explain this co-occurrence.

METHODS

Using data from 6,082 Australian same-sex twin pairs (1,732 monozygotic [MZ] and 1,309 dizygotic [DZ]), ages 23 to 40, we examined prevalence rates of NSSI and SA among twin pairs concordant and discordant for EAU. Conditional logistic regression, controlling for early clinical covariates and the influence of zygosity on EAU, was used to examine the odds ratio (OR) of self-harm within twin pairs discordant for EAU.

RESULTS

Prevalence rates of both NSSI and SA were highest among twin pairs concordant for EAU and for twins who reported EAU within discordant twin pairs. Results from discordant twin analyses revealed nearly 4-fold increased odds of SA for the twin who endorsed EAU, and this OR was equal across MZ and DZ twins. EAU also was associated with elevated odds of NSSI (OR = 7.62), although this was only the case for DZ twins in discordant pairs.

CONCLUSIONS

The equivalent increase in odds of SA for both MZ and DZ twins suggests that causal or individual-specific influences explain the link between EAU and SA. For NSSI, elevated odds for DZ twins and nonsignificant findings for MZ twins implicate correlated genetic factors in the association between EAU and NSSI. Future studies should test mechanisms through which EAU may causally influence SA, as well as examine whether genetic risk for third variables (e.g., negative urgency, stress reactivity) may explain the genetic overlap between EAU and NSSI.

Genetic overlap between alcohol use disorder and bulimic behaviors in European American and African American women

BACKGROUND

Despite substantial evidence that alcohol use disorder (AUD) and bulimic behaviors (i.e., binge eating and compensatory behaviors) co-occur, insufficient information exists regarding a possible shared etiology. Moreover, although numerous twin studies of European ancestry individuals have reported moderate heritability estimates for AUD and bulimic behaviors, with little evidence for shared environmental factors, research on genetic and environmental risk in African American (AA) individuals is lacking.

METHODS

We investigated specific and overlapping genetic and environmental influences on AUD and bulimic behaviors in 3232 European American (EA; 55.38% monozygotic) and 549 AA (42.81% monozygotic) young adult female twins from the Missouri Adolescent Female Twin Study (age range=18-29 years). A structured clinical interview assessed lifetime DSM-5 AUD (minus craving) and bulimic behaviors. Biometrical twin modeling was conducted to generate age-adjusted estimates of genetic and environmental influences on AUD, bulimic behaviors, and their comorbidity.

RESULTS

Estimates of genetic and environmental contributions on AUD and bulimic behaviors could be equated across EA and AA women. Additive genetic effects accounted for 59% (95% CI: 50%, 66%) and 43% (33%, 52%) of the variance in AUD and bulimic behaviors, respectively, with the remainder due to non-shared environmental effects. Shared genetic factors (rg=.33 (.18, .49)) were solely responsible for the correlation between phenotypes; the non-shared environmental correlation was not significant (re=.10 (-.05, .25)).

CONCLUSIONS

Findings indicate similar magnitudes of genetic and environmental effects on AUD and bulimic behaviors for EA and AA women and implicate common genetic mechanisms underlying liability to these problem behaviors.

Frequency of alcohol consumption in humans; the role of metabotropic glutamate receptors and downstream signaling pathways

Rodent models implicate metabotropic glutamate receptors (mGluRs) and downstream signaling pathways in addictive behaviors through metaplasticity. One way mGluRs can influence synaptic plasticity is by regulating the local translation of AMPA receptor trafficking proteins via eukaryotic elongation factor 2 (eEF2). However, genetic variation in this pathway has not been examined with human alcohol use phenotypes. Among a sample of adults living in Detroit, Michigan (Detroit Neighborhood Health Study; n = 788; 83% African American), 206 genetic variants across the mGluR-eEF2-AMPAR pathway (including GRM1, GRM5, HOMER1, HOMER2, EEF2K, MTOR, EIF4E, EEF2, CAMK2A, ARC, GRIA1 and GRIA4) were found to predict number of drinking days per month (corrected P-value < 0.01) when considered as a set (set-based linear regression conducted in PLINK). In addition, a CpG site located in the 3'-untranslated region on the north shore of EEF2 (cg12255298) was hypermethylated in those who drank more frequently (P < 0.05). Importantly, the association between several genetic variants within the mGluR-eEF2-AMPAR pathway and alcohol use behavior (i.e., consumption and alcohol-related problems) replicated in the Grady Trauma Project (GTP), an independent sample of adults living in Atlanta, Georgia (n = 1034; 95% African American), including individual variants in GRM1, GRM5, EEF2, MTOR, GRIA1, GRIA4 and HOMER2 (P < 0.05). Gene-based analyses conducted in the GTP indicated that GRM1 (empirical P < 0.05) and EEF2 (empirical P < 0.01) withstood multiple test corrections and predicted increased alcohol consumption and related problems. In conclusion, insights from rodent studies enabled the identification of novel human alcohol candidate genes within the mGluR-eEF2-AMPAR pathway.